Slot antenna

Abstract

A slot antenna is disclosed for use in RF broadcasting. The antenna includes an elongated longitudinally extending hollow mast surrounding a longitudinal axis. An array of longitudinally spaced slots are formed in the mast for radiating electromagnetic energy therefrom. A coupler bar is associated with each slot. Each coupler bar is located within the mast between the ends of the associated slot for coupling electromagnetic energy from within the mast and developing with the slot a slot-coupler reactance. Tuning means is associated with each slot. Each tuning means is longitudinally spaced from the associated slot. Each tuning means extends inwardly from the mast toward the longitudinal axis for tuning the antenna to reduce the slot-coupler reactance.

Having described the invention, it is now claimed: 
     
       1. A slot antenna for use in RF broadcasting, comprising: a longitudinal axis;   an elongated longitudinally extending hollow mast surrounding said longitudinal axis;   an array of longitudinally spaced slots formed in said mast for radiating electromagnetic energy therefrom;   coupler means associated with each said slot, each said coupler means being located within said mast between the ends of the associated said slot for coupling electromagnetic energy from within said mast and developing with said slot a slot-coupler reactance; and,   tuning means associated with each said slot, each said tuning means being longitudinally spaced from the associated said slot, each said tuning means extending inwardly from said mast toward said longitudinal axis for tuning said antenna to reduce the slot-coupler reactance.   
     
     
       2. A slot antenna as set forth in claim 1 wherein said tuning means includes adjustable probe means for adjustably varying the extent it extends toward said longitudinal axis. 
     
     
       3. A slot antenna as set forth in claim 2 wherein each said tuning means includes a plurality of probe rods. 
     
     
       4. A slot antenna as set forth in claim 3 wherein each said rod is an elongated rod which is threaded about one end and wherein said mast has a threaded aperture associated with each said rod for threadably receiving the threaded end of the associated said rod. 
     
     
       5. A slot antenna as set forth in claim 4 wherein each said rod of each said tuning means is of a different length. 
     
     
       6. A slot antenna as set forth in claim 1 wherein each said coupler means includes a coupler bar having a plurality of guide pins extending therefrom and wherein said mast has a guide pin aperture associated with each said guide pin to assist in properly positioning each said coupler bar in place against said mast. 
     
     
       7. A slot antenna as set forth in claim 6 wherein each said coupler bar is L shaped having a first leg which carries said guide pins and a second leg which extends essentially perpendicular to said first leg and is positioned within said mast over a portion of the length of a said slot. 
     
     
       8. A slot antenna as set forth in claim 1 wherein said antenna includes an elongated inner conductor defining said longitudinal axis. 
     
     
       9. A slot antenna as set forth in claim 8 wherein said mast is an elongated hollow cylinder which coaxially surrounds said inner conductor. 
     
     
       10. A slot antenna as set forth in claim 9 wherein said tuning means includes adjustable probe means for adjustably varying the extent it extends toward said longitudinal axis. 
     
     
       11. A slot antenna as set forth in claim 10 wherein each said tuning means includes a plurality of probe rods. 
     
     
       12. A slot antenna as set forth in claim 11 wherein each said rod is an elongated rod which is threaded about one end and wherein said mast has a threaded aperture associated with each said rod for threadably receiving the threaded end of the associated said rod. 
     
     
       13. A slot antenna as set forth in claim 12 wherein each said rod of each said tuning means is of a different length. 
     
     
       14. A slot antenna as set forth in claim 9 wherein each said coupler means includes a coupler bar having a plurality of guide pins extending therefrom and wherein said mast has a guide pin aperture associated with each said guide pin to assist in properly positioning each said coupler bar in place against said mast. 
     
     
       15. A slot antenna as set forth in claim 14 wherein each said coupler bar is L shaped having a first leg which carries said guide pins and a second leg which extends essentially perpendicular to said first leg and is positioned within said mast over a portion of the length of a said slot. 
     
     
       16. A slot antenna as set forth in claim 15 wherein said coupler bars are identical in size and configuration. 
     
     
       17. A slot antenna for use in RF broadcasting comprising: an elongated longitudinally extending hollow conductive mast having a longitudinal axis, an elongated conductive element extending longitudinally within the mast along the axis, and a plurality of longitudinally spaced slots formed in the mast;   connection means adapted to be connected to a source of RF signals for applying the RF signals to the mast and conductive element;   an RF signal coupler associated with each of the slots, each of the couplers being mounted by fastening devices to the mast, separate couplers being located within the mast adjacent each separate slot for coupling RF electromagnetic energy from within the mast for the radiation the energy from the associated slot, at least one of the couplers having guides that match guides on the mast for controlling the positioning of the coupler while being secured to the mast by the fastening device.   
     
     
       18. A slot antenna as defined in claim 17 wherein the fastening devices are threaded bolts and the guides are pin and hole arrangements. 
     
     
       19. A method of mounting a coupler within a slot antenna that includes an elongated longitudinally extending hollow conductive mast having a longitudinal axis, a plurality of longitudinally spaced slots formed in the mast, a RF signal coupler associated with each of the slots adapted to be mounted to the mast within the mast and adjacent respective slots by fastening devices, the method comprising: providing matching guides located on a coupler and located within the mast adjacent the respective slot to provide a guide mechanism for accurately positioning the coupler at a desired preset location relative to the slot;   inserting the coupler within the mast using the guide to accurately position the coupler at its preset location adjacent its respective slot; and   securing the coupler to the mast with the fastening device while the guides control the placement of the coupler at the preset location relative to the slot.   
     
     
       20. A method of tuning a RF broadcast slot antenna to control slot-coupler reactance, which antenna includes an elongated longitudinally extending hollow conductive outer mast having a longitudinal axis, an elongated conductive element extending longitudinally within the mast along the axis, an elongated conductive element extending longitudinally within the mast along the axis, connection means adapted to be connected to a source of RF signals for applying the RF signals to the mast and conductive element, a plurality of longitudinally spaced slots formed in the mast, a separate RF signal coupler associated with each of the slots adapted to be mounted to the mast thin the mast and adjacent to a respective slot for radiating RF energy from the slot, the method of tuning comprising: providing an adjustable element secured adjacent a slot that extends from the mast into the hollow portion of the mast toward the inner conductor; and   adjusting the amount to which the element extends into the mast to control the slot-coupler reactance.